Tool-holding device



June 5, 1956 5, PENASACK v 2,749,134

TOOL-HOLDING DEVICE Filed March 2, 1953 9 45 INVENTOR. H 6 STEPHEN 1.. PE/VA sAcK "/5 ATTORNEY TOOL-HOLDING DEVICE Stephen L. Penasack, Albion, N. Y., assignor to Carlton G. Lindsay, Perinton, N. Y.

Application March 2, 1953, Serial No. 339,629

4 Claims. (Cl. 279-16) This invention relates to tool-holding devices, and more particularly to devices for holding small tools such as taps, drills, and the like, one object of the invention being to provide an improved tool-holding device having a simpler and more practical construction which may be readily and economically manufactured and assembled.

Another object is to provide a tool-holding device of the above nature which will hold the tool against movement relative thereto under the normal loads encountered, but which will allow the tool to rotate relative thereto, when extra heavy loads are applied to the tool, thereby preventing the tool from being broken by the application of the extra heavy loads.

Another object is to provide a tool-holding device having the above advantages, which may be readily adjusted to accommodate normal working loads of diflerent value, but which will release the tool for rotation relative thereto, when a given normal load on the tool is exceeded.

A further object is to provide a tool-holding device of the above nature in which the holding mechanism is of minimum mass so that in certain instances, such as tapping with small taps, the tool is able to pull the holding device with it as it penetrates further into the workpiece.

Still a further object is to provide a tool-holding device of the above nature which comprises a minimum number of parts which may be readily manufactured and easily assembled by known means.

nited States Patent To these and other ends the invention resides in certain improvements and combinations of parts, all as will be hereinafter more fully described, the novel features being pointed out in the claims at the end of the specification.

In the drawings:

- Fig. l'is a sectional elevation of a tool-holding device embodying the present invention; 1 -'-Fig. 2- is an elevational view o'f-th'e tool-holding device as shown in Fig. 1;

Fig. 3 isan end elevation of the tool-holding device as t shownin Fig. 2; Fig. 4 is a sectional elevation substantially along the line 4-4 in Fig. 1;

Fig. 5 is a sectional elevation substantially along the line 55 in Fig. 1, and

Fig. 6 is a sectional elevation substantially along the similar movement, but is brought into engagement with p the workpiece." The present invention is equally well adapted for use when either the tool or workpiece has a rotary motion, but for the purposes of illustration, its

"function and operation will be described in conjunction with lathe operations where the workpiece is rotated and the tool, while held against rotation, is advanced-by-auto- Patented June 5, 1956 matic or manual means into and out of engagement with the workpiece.

In the past, when tapping, particularly with small taps, on large automatic or semi-automatic lathes, there has been a problem in securing the proper threads in the workpiece without stripping the threads or breaking the tap. That is, if the tap is fed too fast, or too slowly, the result is that the threads being out are stripped and the tapping operation rendered ineffectual. This same holds true in removing the tap from the workpiece, where the rate of movement outwardly from the work must correspond exactly to the pitch of the threads cut into the work. Because of the large mass and inertia of the toolholding devices commonly used, it has been impossible for small taps to pull the toolholder into the work or move it outwardly therefrom when the tool is being removed, as is the case when large taps are used. A further problem that causes frequent breaking of the small taps is the failure of the operator to stop the work when the tap reaches the bottom of the opening, with the result that as the tap can no longer move into the work it is broken by the continual inward force thereon.

I have devised a novel tool-holding device which is of small mass and which is adapted to float on a mount or support so that the tap itself may move the toolholder at the desired speed so as to prevent over or under feeding and thereby prevent stripping of the threads. My improved tool-holding device also has releasable means for holding the tool against rotation relative to the holding device so that when the tap strikes the bottom of the opening and the load thereon increases, the tap is released for rotation with the workpiece. With my improved tool holder it is easy to adjust the tension on the tap holder so that the tap will not rotate as the threads are being cut or as the tap moves outwardly from the work while providing an overload release whereby, if the feeding operation is not stopped at the proper instant and the tap strikes the bottom of the opening, the tap may rotate relative to the holding device rather than breaking, as has been the case in the past.

The preferred embodiment of the present invention, herein disclosed by way of illustration, comprises an arbor 21 (Fig. 1) which is either cylindrical or slightly tapered at one end thereof for mounting in a suitable holding means, such as the turret of an automatic tur- I 'ret" lathe or the tail stock of the manual lathe, as well understood in the art. Arbor 21 is provided with a cap or end plate 23 adjacent the right end thereof which is heldin position by a screw 25 which threadedly engages the right-hand end of the arbor as shown in Fig. 1. Cap 23 is of larger diameter than the right end of arbor 21 and is adapted to engage a seat 27 (Fig. 6) formed in a clutch member 29 for limiting the movement of the clutch member, in one direction, to the right as viewed in Figs. 1, 2 and 6, along the arbor. Clutch member 29 can move from its extreme right-hand position as shown in Fig. 6 to the left until a spring 31 which engages one end of the clutch member and a flange 33 formed on arbor 21, is fully compressed. Spring 31 acts to move and resiliently hold clutch member 29 in its extreme right-hand position as shown in Fig. 6, for purposes hereafter set forth. Arbor 21 is formed with a pair of longitudinally-extending key slots on the outer surface thereof, while clutch member 29 is formed with a similar pair of key slots on the inside thereof which, when keys 35"ar e placed therein, serve as guides for the longitudinal movement of clutch member'29 along arbor 21 while preventing the clutch member from rotating relative to the arbor.

A second clutch member 37 (Fig. 1) is in turn keyed to clutch member 29 by a pair of cylindrical keys 39 (Fig. 6) so that clutch member 37 may move longitudinally along clutch member 29 while being prevented from rotating relative thereto. Clutch member 29 is provided adjacent the right-hand end thereof with an inwardly tapering clutch surface 41 while clutch member 37 is provided adjacent the right-hand end thereof with an inwardly flaring clutch surface 43. Clutch surfaces 41 and 43 are adapted to frictionally engage a pair of complementary-flaring clutch. surfaces 45 and 47 formed on opposite sides of a third clutch member 49. Clutch member 49 is formed with a longitudinally extending bore 51 and means, to be hereafter described, are provided for securely mounting a tool, such as a drill or tap or the like, therein.

Clutch members 29 and 37 are formed adjacent the lefthand ends thereof with a series of mating openings 53 (Fig. circumferentially spaced thcrearound, as shown in Fig. 5. A series of coil springs 55 are placed. within openings 53 and engage at the left-hand end thereof a metallic washer 57 which is held in engagement with. the springs by a split nut 59 threadedly engaging the lefthand end of clutch member 37, as shown in Figs. 1 and 6. A bolt 60 (Fig. 5) is provided to draw opposite parts of nut 59 together and clamp the-same in position on clutch member 37. As nut 59 is turned down on clutch member 37, it compresses springs 55 which in turn draw clutch member 37 leftwardly longitudinally along clutch member 29, thereby bringing clutch surfaces 41 and 43 on clutch members 29 and 37, respectively, into frictional engagement with the corresponding clutch surfaces 45 and 47 on clutch member 49, respectively.

Thus, by turning down nut 59 and compressing springs 55 to a given point, clutch member 49 may be held with sufficient force so as to hold it against rotation under normal loads on the tool attached thereto, while allowing clutch member 49 to slip or rotate relative to members 29 and 37, when the force on the tool exceeds the normal amount.

The means for holding a tool such as a tap or drill within rotatable clutch member 49 preferably comprises a split collet 61 and an externally threaded nut 63 which engages the threads 64 (Fig. 1) formed on the inner surface of clutch member 49. The inner end of collet 61 is preferably formed with a square opening 65 (Fig. 4) therein for closely engaging the end ofthe tool such as a tap, and is split longitudinally thereof into three segments, as well understood in the art. By tightening nut 63, the collet may be compressed so as to securely grip the tool and at the same time the collet and clutch member 49 are securely held together. In order to provide means to hold clutch member 49 against rotation while tightening or loosening nut 63, I preferably provide a depression or hole 66 extending part way through clutch member 49, as shown in Figs. 1 and 6,. and a small opening 67 in. clutch member 37 through which a suitable pin peg may be inserted into engagement with seat 66, thereby securely locking clutch members 39 and 37 together so that nut 63 may be readily tightened or loosened. I also provide a longitudinally-extending oil groove 69 in clutch member 49 which serves to carry oil or other suitable lubrication to clutch faces 45 and 47.

In operation, therefore, arbor 21 is mounted in the turret or tail stock of a lathe and a suitable tool, such as a tap, placed within collet 61 after which nut 63 is tightened to hold the tooland collet in position within clutch member 49. Nut 59 is then turned down increasing the tension on springs 55 and movingclutch member 37 to the left along clutchmember 29, thereby drawing clutch faces 41 and 45, and 43 and 47, respeetively, into clamping engagement and holding. clutch member 49 against rotation so long v as the load on: the tool does not exceed a given value. Nut 59 may be held in the desired adjusted position by tightening clamping bolt 60. Thereafter the tool holder is advanced towards the work, and upon the tap engaging the work, the turret or tail stock is moved towards the work at as nearly as possible the rate at which the tap is moving into the work. However, it is often. ditlicult to synchronize and equalize these rates of movement and, when the arbor and tool holder do not move towards the work as fast as the tap normally would feed, the result is that the threads produced are stripped and the tapping operation rendered ineffectual. My device overcomes this problem in that clutch member 29, upon which the other clutch members are mounted, is arranged for limited longitudinal movement along the arbor so that the arbor may be fed at slightly greater speed than the tap is progressing into the work without forcing the tap and stripping the threads. That is, spring 31 allows the arbor to move inwardly to the right as viewed in Figs. 1 and 6, without exerting any appreciable increase of pressure on the tool-holding device. Thus, starting with spring 31 partially compressed as the tap first engages the workpiece, arbor 21 needs only to be advanced at a rate whereby spring 31 remains in partially compressed condition and clutch member 29 is between its extreme right-hand position, as shown in Fig. l, and its extreme left-hand position where spring 31 is fully compressed. This means that there is a range of allowable feeding speeds for the arbor, which greatly increases the ease of the tapping operation and insures better results. The holding device is of limited mass so that, when even small taps or dies are used, the threads produced have sufficient strength to pull the holder into the work at the proper rate.

When used on a hand-operated lathe, the operator has only to advance the arbor at a sufficient rate to keep spring 31 partially compressed, which means that the holding device is floating on the arbor and can be pulled into the workpiece by the action of the tap or other tool at exactly the proper speed. This same floating action allows for slight variations in the speed with which the tool is removed from the workpiece, for so long as clutch member 29 and associated parts are so positioned on arbor 21- so that spring 31 is only partially compressed, the holding device is again free to float on the arbor and move relative thereto under the interaction of the tool and workpiece.

My invention has a further advantage over previous devices in that the tap will be held against rotation during the cutting of the threads, but when it reaches the bottom of the opening where the load on the tap sharply increases, the tension on springs 55 is such that at this point the load on the tool will exceed the clamping forces of springs 55 and cause clutch member 49 to slip and rotate between fixed clutch members 29 and 37, thereby allowing the tool to be rotated by the work and preventing the breaking of the tool, as has been the. case in the past when the machine was not stopped as soon as the tap reached the bottom of the opening. As nut 59 may be adjusted to vary the tension on springs 55 and thus, on clutch member 49, the toolholder is well adapted for use with a wide range of tools and types of work, and can be set to release the tool when the load thereon exceeds any given value.

A further advantage to my device is that, as both clutch faces 45 and 47 engage correspondingly tapered clutch surfaces 41 and 43, respectively, any wearing of the clutch faces will not throw clutch member 49 out of center, but will merely allow clutch members 37 and 29 to be more tightly clamped together before exerting the necessary clamping force on clutch member 49.

It will thus be seen that the invention accomplishes its objects and, while it has been herein disclosed by reference to the details of. a. preferred embodiment, it is to be understood that such disclosure is intended. in an illustrative. rather than a limiting sense, as it is contemplated that various modifications in the construction and arrangement of the parts will readily occur to those skilled in the art, within the spirit of the invention and the scope of the appended claims.

I claim:

1. A tool-holding device comprising a clutch member having a clutch surface extending at an angle to the longitudinal axis thereof, a second clutch member mounted on said first member for movement longitudinally therealong while being held against rotational movement relative thereto, said second clutch member having a clutch surface extending at an angle to the longitudinal axis thereof, a third clutch member extending between said first two clutch members and having a pair of clutches faces for engaging the respective clutch faces on said first and second clutch members, releasable means for securing a tool to said third clutch member and preventing relative movement therebetween, resilient means engaging said first and second clutch members for moving said members relative to each other for bringing the clutch surfaces thereon into frictional engagement with the respective clutch surfaces on said third clutch member, and manually operable means for adjusting the tension of said resilient means for adjusting the frictional interengagement between said mating pairs of clutch surfaces for holding said third clutch members and tool against rotation relative to said first and second clutch members under normal load while allowing relative rotation between said first and second clutch members and said third clutch member when the tool is subjected to heavier than normal torque loads.

2. A tool-holding device mounted on an arbor adapted to be moved toward and from the work, said device comprising a clutch member mounted for limited longitudinal movement therealong while being held against rotation relative thereto, said clutch member having a clutch surface extending at an angle to the longitudinal axis thereof, a second clutch member mounted on said first member for longitudinal movement therealong while being held against rotational movement relative thereto, said second clutch member having a clutch surface extending at an angle to the longitudinal axis thereof, a third clutch member extending between said first two clutch members and having a pair of clutch faces for engaging the respective clutch faces on said first and second clutch members, releasable means for securing a tool to said third clutch member and preventing relative movement therebetween, and adjustable means for moving said second member relative to said first member for bringing the clutch surfaces thereon into frictional engagement with the respective clutch surfaces on said third clutch member for holding said third clutch member and tool against rotation relative to said first and second clutch members under normal load while allowing said third clutch member and tool to rotate when the tool is sub jected to an extra heavy torque load.

3. A tool-holding device as specified in claim 2 including resilient means engaging said arbor and first clutch member for moving said device along said arbor towards the work.

4. A tool-holding device comprising a clutch member having a clutch surface extending at an angle to the longitudinal axis thereof, a second clutch member mounted on said first member for longitudinal movement therealong while being held against rotational movement relative thereto, said second clutch member having a clutch surface extending at an angle to the longitudinal axis thereof, a third clutch member extending between said first two clutch members and having a pair of clutch faces for engaging the respective clutch faces on said first and second clutch members, said third clutch member being formed with a recessed bore extending longitudinally inwardly from the outer end thereof, a split collet adapted to fit in the bore of said third clutch member for holding a tool in said third clutch member, a clamping member threadedly engaging said third clutch member for holding said collet in fixed position in said third clutch member and clamping the tool in said collet, and adjustable means for moving said second member relative to said first member for bringing the clutch surfaces thereon into frictional engagement with the respective clutch surfaces on said third clutch member for holding said third clutch member and tool against rotation relative to said first and second clutch members under normal load while allowing said third clutch member and tool to rotate relative to said first and second clutch members when the tool is subjected to an extra heavy torque load.

References Cited in the file of this patent UNITED STATES PATENTS 235,283 Olin Dec. 7, 1880 717,199 Hollm Dec. 30, 1902 2,527,517 Barker et a1. Oct. 31, 1950 2,570,752 Benjamin et al. Oct. 9, 1951 

